Dauby, P.

Davoult, D.

De Bettignies, F.

Lepoint, G.

Open Marine Archive

 -  121  -  
Oral presentation General session 
Trophic subsidy through ecosystems: role and dynamics of nearshore 
subtidal detrital accumulations of Laminaria hyperborea 
De Bettignies Florian
1
, Dauby Patrick
2
, Lepoint Gilles
3
 and Davoult Dominique
1
 
1
  UMR 7144 AD2M, Roscoff Marine Station, Sorbonne University, Place Georges Teissier, F-29680 
Roscoff, France  
 E-mail: fdebettignies@sb-roscoff.fr 
2
  Laboratory of Systematics and Animal Diversity, MARE Center, University of Liège, Sart Tilman B6C, 
4000 Liege, Belgium 
3
  Laboratory of Oceanography, MARE Center, University of Liège, Sart Tilman B6C, 4000 Liege, Belgium 
 
Kelps are major foundation species that support one of the most productive habitats in coastal 
environments (1-2 kgC.m
-2
.yr
-1
).  Despite kelp forests being extensively studied in term of biodiversity 
and ecological functioning; the area of influence of such productive ecosystem is largely underestimated 
and remains little-understood. In Europe, the dominant kelp species, Laminaria hyperborea, is not hardly 
influenced by grazing and a major part of the biomass is exported via erosion, old-frond detachment or 
dislodgment. Kelp accumulations are observed on the coast as beach wracks but also offshore in benthic 
habitats where debris settle depending on topography (depressions, canyons) or current. Kelps supply 
adjacent habitats in organic matter and constitute a source for external food webs. “Hotspots” of 
secondary benthic production arise when detritus accumulates. To describe the degradation dynamics 
of L. hyperborea accumulations and to investigate the role played by the debris in structuring adjacent 
habitats and benthic communities, two six-month litter-bag experiments have been deployed in-situ. We 
used a multidisciplinary approach combining community ecology, trophic ecology (stable isotopes), 
biochemistry (chemical defenses), physiology (PAM and respiration proxy) and microbiology. According 
to the experimental depth, L. hyperborea degradation is a slow process leading to an average biomass 
loss of 15%.month
-1
. The large fragments remain visually fresh and respond to light stimuli (PAM) after 
5-6 months of degradation. These results suggest that L. hyperborea, even dislodged and exported could 
still fulfil the primary-producer function after several months. At the same time, kelp tissues are rapidly 
colonized by macrofauna and a relatively complex multitrophic ecological succession develops after 3-4 
months. Kelp forests are important habitat modifiers and through the process of export and 
accumulation can impact a variety of subtidal ecosystems. 
 
Keywords: kelp beds; degradation; production; connectivity; stable isotopes 
  


Trophic subsidy through ecosystems: role and dynamics of nearshore subtidal detrital accumulations of <i>Laminaria hyperborea</i>

http://www.vliz.be/imisdocs/publications/318320.pdf

Trophic subsidy through ecosystems: role and dynamics of nearshore subtidal detrital accumulations of <i>Laminaria hyperborea</i>

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